Electrically erasable programmable read-only memory cell and memory device and manufacturing method thereof

ABSTRACT

A manufacturing method and a device of an EEPROM cell are provided. The method includes the following steps. First, a tunnel layer and an inter-gate dielectric layer are formed over a surface of a substrate respectively, and a doped region is formed in the substrate under the inter-gate dielectric layer and used as a control gate. Thereafter, a floating gate is formed over the inter-gate dielectric layer and the tunnel layer. Thereafter, a source region and a drain region are formed in the substrate beside two sides of the floating gate under the tunnel layer. Especially, the manufacturing method of the memory cell can be integrated with the manufacturing process of high operation voltage component and low operation voltage component.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a memory device and a manufacturingmethod thereof. More particularly, the present invention relates to anelectrically erasable programmable read-only memory (EEPROM) cell andmemory device that can be compatible with high operational voltagecomponent and low operational voltage component, and the manufacturingmethod thereof.

2. Description of Related Art

Conventionally, electrically erasable programmable read-only memory(EEPROM) has the advantages of being programmable, erasable and thestored data being retainable even the power to the device is removed. Inaddition, EEPROM is also a kind of non-volatile memory. Therefore,EEPROM is very suitable for being integrated in a logic or mixed modeintegrated circuits (IC) to enhance the auto-recovery or auto-adjustmentfunction of the logic or mixed mode IC.

FIG. 1A and FIG. 1B are schematic cross-sectional views illustrating amanufacturing process of a conventional EEPROM. Referring to FIG. 1A, inthe manufacturing process of a conventional EEPROM, a tunnel layer 102,a polysilicon floating gate layer 104, an inter-gate dielectric layer106 and a polysilicon control gate layer 108 are formed on a substrate100 sequentially. Then, referring to FIG. 1B, the layers described aboveare patterned to form a stacked gate structure 110, and a source region112 a and a drain region 112 b are formed in the substrate 100 besidetwo sides of the stacked gate structure 110.

However, in the manufacturing process described above, at least twopolysilicon layers shall be disposed to form the floating gate and thecontrol gate respectively. In addition, the two polysilicon layers ofthe memory cell and the gate of the metal oxide semiconductor (MOS)component of the peripheral circuit area are not at the same level ofheight. Therefore, the integration of the memory cell with theperipheral circuit is difficult.

In addition, the operation voltage of a conventional EEPROM is generallyless than 12V. Therefore, the integration of EEPROM with highoperational voltage component and low operational voltage component isdifficult.

Furthermore, a conventional EEPROM cell is generally formed in anisolated well region; thus the EEPROM cell may be operatedindependently. Accordingly, the EEPROM cell can not share the same wellregion with the high operational voltage component and the lowoperational voltage component. Therefore, it is difficult to integratean EEPROM cell with high operational voltage component and lowoperational voltage component.

SUMMARY OF THE INVENTION

Therefore, the present invention is directed to a manufacturing methodof an EEPROM cell that can be easily integrated with the manufacturingprocess of the component of the peripheral circuit because the gateheight of the EEPROM cell is similar to that of the peripheral circuit.

In addition, the present invention is directed to an EEPROM cell havinga novel structure being different from the conventional memory structureconstructed by two polysilicon layers.

Moreover, the present invention is directed to a manufacturing method ofa memory device for solving the problem that the process of theconventional EEPROM cell can not be integrated with the process of thehigh operational voltage component and the low operational voltagecomponent.

Furthermore, the present invention is directed to a memory device forsolving the problem that the conventional EEPROM cell can not beincorporated with the high operational voltage component and the lowoperational voltage component.

According to one embodiment of the present invention, a manufacturingmethod of an EEPROM cell is provided. The method comprises, for examplebut not limited to, the following steps. First, a tunnel layer and aninter-gate dielectric layer are formed over a surface of a substraterespectively. Then, a doped region is formed in the substrate under theinter-gate dielectric layer and used as a control gate. Thereafter, afloating gate is formed over the inter-gate dielectric layer and thetunnel layer. A source region and a drain region are further formed inthe substrate beside two sides of the floating gate under the tunnellayer.

According to one embodiment of the present invention, an EEPROM cell isprovided. The EEPROM cell comprises a substrate, an inter-gatedielectric layer, a tunnel layer, a doped region, a floating gate, asource region and a drain region. The inter-gate dielectric layer andthe tunnel layer are disposed over a surface of the substraterespectively. In addition, the doped region is disposed in the substrateunder the inter-gate dielectric layer, and is used as a control gate.Moreover, the floating gate is disposed over the tunnel layer and theinter-gate dielectric layer. In addition, the source region and thedrain region are disposed in the substrate at two sides of the floatinggate under the tunnel layer.

Moreover, according to one embodiment of the present invention, amanufacturing method of a memory device is provided. The methodcomprises, for example but not limited to, the following steps. First, asubstrate comprising a memory cell area and a peripheral circuit area isprovided. The peripheral circuit area comprises a high operationalvoltage component area and a low operational voltage component area.Thereafter, a tunnel layer and an inter-gate dielectric layer are formedover a surface of the substrate of the memory cell area respectively.Then, a first inter-gate dielectric layer and a second inter-gatedielectric layer are formed over a surface of the substrate of the highoperational voltage component area and the low operational voltagecomponent area of the peripheral circuit area respectively. A dopedregion is formed in the substrate under the inter-gate dielectric layerand used as a control gate. Then, a floating gate is formed over theinter-gate dielectric layer and the tunnel layer in the memory cellarea, and a first gate and a second gate are formed over the firstinter-gate dielectric layer and the second inter-gate dielectric layerin the peripheral circuit area respectively. Thereafter, a first sourceregion and a first drain region are formed in the substrate beside twosides of the floating gate under the tunnel layer of the memory cellarea. In the peripheral circuit area, a second source region and asecond drain region are formed in the substrate beside two sides of thefirst gate, and a third source region and a third drain region areformed in the substrate beside two sides of the second gate.

In addition, according to one embodiment of the present invention, amemory device is provided. The memory device comprises, for example butnot limited to, a substrate, at least a memory cell, at least a highoperational voltage component and at least a low operational voltagecomponent. The substrate comprises a memory cell area and a peripheralcircuit area. The peripheral circuit area comprises a high operationalvoltage component area and a low operational voltage component area. Inaddition, the memory cell is disposed in the memory cell area, andcomprises an inter-gate dielectric layer, a tunnel layer, a dopedregion, a floating gate, a first source region and a first drain region.The inter-gate dielectric layer and the tunnel layer are disposed over asurface of the substrate respectively. In addition, the doped region isdisposed in the substrate under the inter-gate dielectric layer, and isused as a control gate. Moreover, the floating gate is disposed over thetunnel layer and the inter-gate dielectric layer. In addition, the firstsource region and the first drain region are disposed in the substratebeside two sides of the floating gate under the tunnel layer. Moreover,the high operational voltage component is disposed in the highoperational voltage component area, and comprises a first inter-gatedielectric layer, a first gate, a second source region and a seconddrain region. The first inter-gate dielectric layer is disposed over asurface of the substrate of the high operational voltage component area.In addition, the first gate is disposed over the first inter-gatedielectric layer. Moreover, the second source region and the seconddrain region are disposed in the substrate at two sides of the firstgate. In addition, the low operational voltage component is disposed inthe low operational voltage component area, and comprises a secondinter-gate dielectric layer, a second gate, a third source region and athird drain region. The second inter-gate dielectric layer is disposedover a surface of the substrate of the low operational voltage componentarea. Moreover, the second gate is disposed over the second inter-gatedielectric layer. In addition, the third source region and the thirddrain region are disposed in the substrate beside two sides of thesecond gate.

Accordingly, since the control gate of the EEPROM cell of the presentinvention is disposed in the substrate as a doped region, the structureof the EEPROM cell of the present invention is novel and different fromthe structure of the conventional memory cell having two polysiliconlayers. In addition, the memory cell of the present invention can beintegrated with the high operational voltage component and the lowoperational voltage component.

One or part or all of these and other features and advantages of thepresent invention will become readily apparent to those skilled in thisart from the following description wherein there is shown and describeda preferred embodiment of this invention, simply by way of illustrationof one of the modes best suited to carry out the invention. As it willbe realized, the invention is capable of different embodiments, and itsseveral details are capable of modifications in various, obvious aspectsall without departing from the invention. Accordingly, the drawings anddescriptions will be regarded as illustrative in nature and not asrestrictive

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are intended to provide further understandingof the invention, and are incorporated in and constitute a part of thisspecification. The drawings illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1A and FIG. 1B are schematic cross-sectional views illustrating amanufacturing process of a conventional EEPROM.

FIG. 2A to FIG. 2D are cross-sectional views illustrating amanufacturing process of a memory device according to one embodiment ofthe present invention.

FIG. 3 is a schematic top view illustrating an EEPROM cell of a memorycell area of FIG. 2A to FIG. 2D, wherein the cross-sectional view of theleft side of the memory cell area 202 of FIG. 2A to FIG. 2D is along theline I-I′ of FIG. 3, and the cross-sectional view of the right side ofthe memory cell area 202 of FIG. 2A to FIG. 2D is along the line II-II′of FIG. 3.

FIG. 4 is a cross-sectional view of an EEPROM cell according to oneembodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention is described in detail hereinafter with referenceto the accompanying drawings, in which preferred embodiments of theinvention are illustrated. The present invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout.

It is noted that, in the invention, the high operational voltagecomponent represents a component operated under a relative high voltage,and the low operational voltage component represents a componentoperated under a relative low voltage. The relative high voltage and therelative low voltage are decided by the actual situation of theoperation; however, the relative high voltage is larger that therelative low voltage.

FIG. 2A to FIG. 2D are cross-sectional views illustrating amanufacturing process of a memory device according to one embodiment ofthe present invention. The memory device comprises an EEPROM disposed inmemory cell area and a high operational voltage component and a lowoperational voltage component disposed in peripheral circuit area. Inaddition, FIG. 3 is a schematic top view illustrating an EEPROM cell ofa memory cell area of FIG. 2A to FIG. 2D. The cross-sectional view ofthe left side of the memory cell area 202 of FIG. 2A to FIG. 2D is alongthe cutting line I-I′ of FIG. 3. The cross-sectional view of the rightside of the memory cell area 202 of FIG. 2A to FIG. 2D is along thecutting line II-II′ of FIG. 3.

Referring to FIG. 2A and FIG. 3, in the method of manufacturing thememory device of the present invention, for example, a substrate 200having a memory cell area 202 and a peripheral circuit area 204 isprovided first. The peripheral circuit area 204 comprises, for examplebut not limited to, a high operational voltage component area 206 and alow operational voltage component area 208.

In one embodiment of the present invention, the high operational voltagecomponent area 206 further comprises, for example, an n-type highoperational voltage component area 210 a and a p-type high operationalvoltage component area 210 b. The low operational voltage component area208 further comprises, for example, an n-type low operational voltagecomponent area 212 a and a p-type low operational voltage component area212 b.

In addition, in one embodiment of the present invention, the areasdescribed above are, for example but not limited to, defined bycomponent isolation area 214. The component isolation area 214 is, forexample but not limited to, formed by local oxidation (LOCOS) process,shallow trench isolation (STI) process or other applicable process.

Thereafter, a tunnel layer and an inter-gate dielectric layer are formedover the surface of the substrate 200 of the memory cell area 202respectively. Two inter-gate dielectric layers are formed over thesurface of the substrate 200 of the high operational voltage componentarea 206 and the low operational voltage component area 208 of theperipheral circuit area 204 respectively. A doped region is formed inthe substrate 200 under the inter-gate dielectric layer and used as acontrol gate. In one embodiment of the present invention, the filmlayers and doped regions described above are formed by, for example butnot limited to, the steps illustrated in FIG. 2A to FIG. 2C.

Referring to FIG. 2A, a dielectric material layer 216 is formed over thesubstrate 200. The material of the dielectric material layer 216comprises, for example but not limited to, silicon oxide or otherapplicable material. The dielectric material layer 216 is, for examplebut not limited to, formed by thermal oxidation process or otherapplicable process. The thickness of the dielectric material layer 216is, for example but not limited to, between about 30 nm to about 50 nm.

In one embodiment of the present invention, before the dielectricmaterial layer 216 is formed, further comprises forming a p-type wellregion 218 and an n-type well region 220 in the substrate 200 of thememory cell area 202 and the peripheral circuit area 204. The wellregions 218 and 220 are formed by, for example but not limited to, ionimplant process. The p-type well region 218 of the peripheral circuitarea 204 is formed in the substrate 200 of the n-type high operationalvoltage component area 210 a and the n-type low operational voltagecomponent area 212 a. The n-type well region 220 is formed in thesubstrate 200 of the p-type high operational voltage component area 210b and the p-type low operational voltage component area 212 b.

Thereafter, an n-type doped region 222 is formed in the well region 220of the memory cell area 202 and used as a control gate. The n-type dopedregion 222 is formed by, for example but not limited to, ion implantprocess. In one embodiment of the present invention, during the n-typedoped region 222 is formed, further comprises forming another n-typedoped region 223 in the substrate 200 under the component isolation area214 of the p-type high operational voltage component area 210 b. Then-type doped region 223 may be, for example, used as a channel stop.

In addition, in one embodiment of the present invention, after then-type doped region 222 is formed, the method further comprises forminga doped region 224 in the p-type well region 218 of the n-type highoperational voltage component area 210 a to adjust the dopantconcentration of the predetermined channel area. Therefore, thethreshold voltage of the high operational voltage component is adjusted.Moreover, in one embodiment of the present invention, after the n-typedoped region 222 is formed, the method further comprises forming a dopedregion 226 in the n-type well region 220 of the p-type high operationalvoltage component area 210 b to adjust the dopant concentration of thepredetermined channel area. Therefore, the threshold voltage of the highoperational voltage component is adjusted.

Then, referring to FIG. 2B, the dielectric material layer 216 over thep-type well region 218 in the memory cell area 202 is removed, and thedielectric material layer 216 over the surface of the substrate 200 ofthe low operational voltage component area 208 is removed. Therefore, aportion of the surface of the substrate 200 is exposed. The portion ofthe dielectric material layer 216 is removed by, for example but notlimited to, dry etching process, wet etching process or other applicableprocess. A portion of the residual dielectric material layer 216 in thememory cell area 202 is used as an inter-gate dielectric layer 228, anda portion of the residual dielectric material layer 216 over the highoperational voltage component area 206 is used as an inter-gatedielectric layer 230.

In one embodiment of the present invention, before a portion of thedielectric material layer 216 is removed, the method further comprisesforming a doped region 232 as a channel stop in the substrate 200 underthe component isolation area 214 of the n-type high operational voltagecomponent area 210 a. In addition, in one embodiment of the presentinvention, before a portion of the dielectric material layer 216 isremoved, the method further comprises forming a doped region (not shown)as a channel stop and an anti-punch through junction surface in then-type low operational voltage component area 212 a and the memory cellarea 202.

Moreover, in one embodiment of the present invention, before a portionof the dielectric material layer 216 is removed, the method furthercomprises forming a doped region 236 in the p-type well region 218 ofthe memory cell area 202, forming a doped region 238 in the p-type wellregion 218 of the n-type low operational voltage component area 212 a ofthe peripheral circuit area 204, and forming a doped region 240 in then-type well region 220 of the p-type low operational voltage componentarea 212 b. Therefore, the dopant concentration of the predeterminedchannel area is adjusted, and the threshold voltage of the memory deviceand the low operational voltage component are adjusted.

Then, a dielectric material layer 242 is formed over the substrate 200.The material of the dielectric material layer 242 comprises, for examplebut not limited to, silicon oxide or other applicable material. Thedielectric material layer 242 is formed by, for example but not limitedto, thermal oxidation process or other applicable process. The thicknessof the dielectric material layer 242 is, for example but not limited to,between about 6 nm to about 8 nm. In the meanwhile, the thickness of theinter-gate dielectric layer 230 and the inter-gate dielectric layer 228is also increased.

Then, referring to FIG. 2C, the dielectric material layer 242 of the lowoperational voltage component area 208 is removed to expose a portion ofthe surface of the substrate 200. The residual dielectric material layer242 in the memory cell area 202 is used as a tunnel layer 244. A portionof the dielectric material layer 242 is removed by, for example but notlimited to, dry etching process, wet etching process or other applicableprocess.

Thereafter, a dielectric material layer (not shown) is formed over thesubstrate 200, wherein a portion of the dielectric material layer formedin the low operational voltage component area 208 is used as aninter-gate dielectric layer 246. The material of the dielectric materiallayer comprises, for example but not limited to, silicon oxide or otherapplicable material. The dielectric material layer is formed by, forexample but not limited to, thermal oxidation process or otherapplicable process. The thickness of the dielectric material layer is,for example but not limited to, between about 6 nm to about 7 nm. Atthis moment, the thicknesses of the inter-gate dielectric layer 230, theinter-gate dielectric layer 228 and the tunnel layer 244 are alsoincreased. In one embodiment of the present invention, the thickness ofthe inter-gate dielectric layer 228 of the memory cell area 202 isgreater than the thickness of the tunnel layer 244. The thickness of theinter-gate dielectric layer 228 is, for example but not limited to,between about 30 nm to about 50 nm. The thickness of the tunnel layer244 is, for example but not limited to, between about 9.5 nm to about 10nm. In addition, the thickness of the inter-gate dielectric layer 230 ofthe high operational voltage component area 206 is, for example but notlimited to, larger than the thickness of the inter-gate dielectric layer246 of the low operational voltage component area 208. Therefore, thecomponent formed in the high operational voltage component area 206 maybe applied with higher voltage. The thickness of the inter-gatedielectric layer 230 is, for example but not limited to, between about45 nm to about 50 nm. The thickness of the inter-gate dielectric layer246 is, for example but not limited to, between about 6 nm to about 7nm.

Then, a floating gate 248 is formed over the inter-gate dielectric layer228 and the tunnel layer 244 of the memory cell area 202, and gates 250and 252 are formed over the inter-gate dielectric layer 230 and theinter-gate dielectric layer 246 of the peripheral circuit area 204respectively. The material of the floating gate 248 and gates 250 and252 comprises, for example but not limited to, polysilicon, dopedpolysilicon, metal silicide or other applicable conductive material. Themetal silicide comprises, for example but not limited to, tungstensilicide. In addition, the floating gate 248 and gates 250 and 252 areformed by, for example but not limited to, conventional manufacturingprocess of gate.

In one embodiment of the present invention, after the floating gate 248and gates 250 and 252 are formed, the method further comprises formingan n-type deeply doped region 254 and a p-type deeply doped region 256in the substrate 200 at two sides of the gate 250 of the n-type highoperational voltage component area 210 a and the p-type high operationalvoltage component area 210 b respectively. Therefore, the breakdownvoltage of the high operational voltage component is increased.

In addition, in one embodiment of the present invention, after thefloating gate 248 and the gates 250 and 252 are formed, the methodfurther comprises forming an n-type deeply doped region 257 in the dopedregion 236 memory cell area 202 of the p-type well region 218 under thetunnel layer 244. Therefore, the breakdown voltage at the sourceterminal of the memory device is increased.

Then, referring to FIG. 2D, an n-type source region 258 a and a drainregion 258 b are formed in the substrate 200 beside two sides of thefloating gate 248 under the tunnel layer 244 in the memory cell area202. An n-type source region 260 a and a drain region 260 b are formedin the deeply doped region 254 beside two sides of the gate 250 in then-type high operational voltage component area 210 a. An n-type sourceregion 262 a and a drain region 262 b are formed in the doped region 238beside two sides of the gate 252 in the n-type low operational voltagecomponent area 212 a. A p-type source region 264 a and a drain region264 b are formed in the deeply doped region 256 beside two sides of thegate 250 in the p-type high operational voltage component area 210 b. Ap-type source region 266 a and a drain region 266 b are formed in thedoped region 240 beside two sides of the gate 252 in the p-type lowoperational voltage component area 212 b. The source region and thedrain region described above are formed by, for example but not limitedto, ion implant process using p-type dopant and/or n-type dopant.

In one embodiment of the present invention, during the n-type sourceregion and drain region are formed, the method further comprises formingan n-type densely doped region 268 in the doped region 222 beside thefloating gate 248 of the memory cell area 202. The n-type densely dopedregion 268 may be used as a portion of the control gate to increase theconductivity of the control gate.

In addition, in one embodiment of the present invention, before or afterthe source region and the drain region are formed, the method furthercomprises forming a lightly doped drain region (not shown) in thesubstrate 200 beside two sides of the floating gate 248 and the gates250 and 252. Therefore, the dopant concentration of the source regionand the drain region can be adjusted. The lightly doped drain region isformed by, for example but not limited to, pocket type ion implantprocess or conventional ion implant process using the spacer 270 formedon the sidewall of the floating gate 248 and the gates 250 and 252 asmask.

After the source region and the drain region described above are formed,the method further comprises performing an annealing process to thesource region and the drain region, and then performing a relatedinterconnection process. Since those skilled in the art are acquaintedwith the interconnection process, it will not be described in detail.

Hereinafter, the structure formed in the method of the present inventiondescribed above will be described. Referring to FIG. 2D and FIG. 3, thememory device of the present invention comprises, for example but notlimited to, a substrate 200, at least a memory cell, at least a highoperational voltage component and at least a low operational voltagecomponent. The substrate 200 comprises a memory cell area 202 and aperipheral circuit area 204, the peripheral circuit area 204 comprises ahigh operational voltage component area 206 and a low operationalvoltage component area 208, wherein these areas are mutually separatedby component isolation area 214.

In one embodiment of the present invention, the high operational voltagecomponent area 206 further comprises an n-type high operational voltagecomponent area 210 a and a p-type high operational voltage componentarea 210 b. The low operational voltage component area 208 furthercomprises an n-type low operational voltage component area 212 a and ap-type low operational voltage component area 212 b. In addition, in oneembodiment of the present invention, the substrate 200 further comprisesa plurality of p-type well regions 218 and a plurality of n-type wellregions 220. The p-type well region 218 in the peripheral circuit area204 is disposed in the substrate 200 of the n-type high operationalvoltage component area 210 a and the n-type low operational voltagecomponent area 212 a. The n-type well region 220 in the peripheralcircuit area 204 is disposed in the substrate 200 of the p-type highoperational voltage component area 210 b and the n-type low operationalvoltage component area 212 b.

Moreover, the memory cell is disposed in the memory cell area 202 andcomprises an inter-gate dielectric layer 228, a tunnel layer 244, adoped region 222, a floating gate 248, a source region 258 a and a drainregion 258 b. The inter-gate dielectric layer 228 and the tunnel layer244 are respectively disposed over the surface of the substrate 200 ofthe memory cell area 202. The thickness of the inter-gate dielectriclayer 228 is greater than the thickness of the tunnel layer 244, and is,for example but not limited to, between about 30 nm to about 50 nm. Thethickness of the tunnel layer 244 is, for example but not limited to,between about 9.5 nm to about 10 nm.

In addition, the doped region 222 is disposed in the n-type well region220 under the inter-gate dielectric layer 228, and is used as a controlgate. The dopant of the doped region 222 comprises, for example but notlimited to, an n-type dopant.

Moreover, the floating gate 248 is disposed over the tunnel layer 244and the inter-gate dielectric layer 228. The source region 258 a and thedrain region 258 b are disposed in the substrate 200 beside two sides ofthe floating gate 248 over the tunnel layer 244.

In one embodiment of the present invention, the memory cell furthercomprises a densely doped region 268 disposed in the doped region 222beside the floating gate 248 of the memory cell area 202. The denselydoped region 268 may be a portion of the control gate to increase theconductivity of the control gate. In addition, in one embodiment of thepresent invention, the memory cell further comprises a doped region 236disposed in the p-type well region 218, wherein the source region 258 aand the drain region 258 b are disposed in the doped region 236.Therefore, the dopant concentration of the channel area may be adjusted,and further the threshold voltage of the memory device may also beadjusted. Moreover, in one embodiment of the present invention, thememory cell further comprises a deeply doped region 257 disposed in thedoped region 236 under the tunnel layer 244. The source region 258 a isdisposed in the deeply doped region 257 to increase the breakdownvoltage at the source terminal of the memory device.

Moreover, the high operational voltage component is disposed in the highoperational voltage component area 206 and comprises an inter-gatedielectric layer 230, a gate 250, source regions 260 a and 264 a anddrain regions 260 b and 264 b. The inter-gate dielectric layer 230 isdisposed over the surface of the substrate 200 of the high operationalvoltage component area 206. The gate 250 is disposed over the inter-gatedielectric layer 230.

In addition, the source region 260 a and the drain region 260 b aredisposed in the substrate 200 beside two sides of the gate 250 of then-type high operational voltage component area 210 a. The dopant of thesource region 260 a and the drain region 260 b comprises n-type dopant.Moreover, the source region 264 a and the drain region 264 b aredisposed in the substrate 200 at two sides of the gate 250 of the p-typehigh operational voltage component area 210 b. The dopant of the sourceregion 264 a and the drain region 264 b comprises p-type dopant.

In one embodiment of the present invention, the high operational voltagecomponent further comprises doped regions 224 and 226 disposed in thep-type well region 218 and the n-type well region 220 respectively. Thesource region 260 a, the drain region 260 b, the source region 264 a andthe drain region 264 b may be disposed in the doped regions 224 and 226respectively to adjust the dopant concentration of the channel area.Therefore, the threshold voltage of the high operational voltagecomponent is adjusted. Moreover, the high operational voltage componentfurther comprises deeply doped regions 254 and 256 disposed in thep-type well region 218 and the n-type well region 220 beside two sidesof the gate 250 respectively. The source region 260 a, the drain region260 b, the source region 264 a and the drain region 264 b may bedisposed in the deeply doped regions 254 and 256 respectively toincrease the breakdown voltage of the high operational voltagecomponent. Moreover, the high operational voltage component furthercomprises doped regions 232 and 223, disposed in the substrate 200 underthe component isolation area 214 of the p-type well region 218 and then-type well region respectively, and is used as a channel stop.

Moreover, the low operational voltage component is disposed in the lowoperational voltage component area 208, and comprises an inter-gatedielectric layer 246, a gate 252, source regions 262 a and 266 a anddrain regions 262 b and 266 b. The inter-gate dielectric layer 246 isdisposed over the surface of the substrate 200 of the low operationalvoltage component area 208. In addition, the thickness of the inter-gatedielectric layer 230 of the high operational voltage component area 206is greater than the thickness of the inter-gate dielectric layer 246 ofthe low operational voltage component 208. Therefore, the componentformed in the high operational voltage component area 206 may be appliedwith higher voltage. The thickness of the inter-gate dielectric layer230 is, for example but not limited to, between about 45 nm to about 50nm. The thickness of the inter-gate dielectric layer 246 is, for examplebut not limited to, between about 6 nm to about 7 nm.

In addition, the gate 252 is disposed over the inter-gate dielectriclayer 246. Moreover, the source region 262 a and the drain region 262 bare disposed in the substrate 200 beside two sides of the gate 252 ofthe n-type low operational voltage component area 212 a. The dopant ofthe source region 262 a and the drain region 262 b comprises an n-typedopant. In addition, the source region 266 a and the drain region 266 bare disposed in the substrate 200 beside two sides of the gate 252 ofthe p-type low operational voltage component area 212 b. The dopant ofthe source region 266 a and the drain region 266 b comprises a p-typedopant.

In one embodiment of the present invention, the low operational voltagecomponent further comprises doped regions 238 and 240 disposed in thep-type well region 218 and the n-type well region 220 respectively. Thesource region 262 a, the drain region 262 b, the source region 266 a anddrain region 266 b are disposed in the doped regions 238 and 240respectively to adjust the dopant concentration of the channel area.Therefore, the threshold voltage of the low operational voltagecomponent is adjusted.

It is noted that, the method and the device of the present invention isnot limited to the embodiments of the present invention described above.For example, the EEPROM cell (e.g., as shown in FIG. 4) of the memorydevice may be integrated with another kind of circuits or componentsexcept for the high operational voltage component or the low operationalvoltage component of the peripheral circuit area described above.

Therefore, the method of forming an EEPROM cell of the present inventioncomprises, for example but not limited to, the following steps. First, atunnel layer 244 and an inter-gate dielectric layer 228 are formed overthe surface of the substrate 200 respectively. Then, a doped region 222is formed in the substrate 200 under the inter-gate dielectric layer 228and used as a control gate. Thereafter, a floating gate 248 is formedover the inter-gate dielectric layer 228 and the tunnel layer 244. Asource region 258 a and a drain region 258 b are further formed in thesubstrate 200 beside two sides of the floating gate 248 under the tunnellayer 244. Therefore, the EEPROM cell formed by the method abovecomprises a substrate 200, an inter-gate dielectric layer 228, a tunnellayer 244, a doped region 222, a floating gate 248, a source region 258a and a drain region 258 b. The inter-gate dielectric layer 228 and thetunnel layer 244 are disposed over a surface of the substrate 200respectively. In addition, the doped region 222 is disposed in thesubstrate 200 under the inter-gate dielectric layer 228, and used as acontrol gate. Moreover, the floating gate 248 is disposed over thetunnel layer 244 and the inter-gate dielectric layer 228. In addition,the source region 258 a and the drain region 258 b are disposed in thesubstrate 200 at two sides of the floating gate 248 under the tunnellayer 244.

Accordingly, the present invention has the advantages described below.First, the structure of the memory cell of the present invention isnovel since the EEPROM cell of the present invention is formed in then-type well region and the p-type well region, and the control gate isformed in the substrate as a doped region. Furthermore, in the EEPROMcell of the present invention, only the floating gate is formed over thesubstrate. The control gate formed in the substrate as a doped region.Therefore, the integration of the EEPROM cell of the present inventionwith the component having a single gate in the general peripheralcircuit area is easy. In addition, in the EEPROM cell of the presentinvention, the inter-gate dielectric layer is much thicker, and thesource region is formed in the deeply doped region. Therefore, theEEPROM cell of the present invention may integrate with the highoperational voltage component and the low operational voltage component.In other words, the EEPROM cell of the present invention may operatebetween, for example but not limited to, about 10V to about 20V and thusmay integrate with the high operational voltage component. In addition,the EEPROM cell of the present invention may also operate between, forexample but not limited to, about 3V to about 6V, and thus may integratewith the low operational voltage component.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without changing the scope or departing from the spirit of thepresent invention. In view of the foregoing, it is intended that thepresent invention cover modifications and variations of this inventionprovided they fall within the scope of the following claims and theirequivalents.

1. A manufacturing method of an electrically erasable programmableread-only memory (EEPROM) cell, comprising: providing a substrate;forming a first well region and a second well region, with differenceconductive type each other, in the substrate; forming a tunnel layer andan inter-gate dielectric layer over a surface of the substraterespectively; forming a doped region used as a control gate in thesubstrate under the inter-gate dielectric layer; forming a floating gateover the inter-gate dielectric layer and the tunnel layer, wherein thefloating gate is formed over the first well region and the second wellregion; and forming a source region and a drain region in the substratebeside two sides of the floating gate under the tunnel layer.
 2. Themethod of claim 1, wherein a thickness of the inter-gate dielectriclayer is greater than a thickness of the tunnel layer.
 3. The method ofclaim 1, wherein a thickness of the inter-gate dielectric layer is in arange of about 30 nm to about 50 nm.
 4. The method of claim 1, whereinthe tunnel layer is formed on a surface of the first well region, theinter-gate dielectric layer is formed on a surface of the second wellregion, and the doped region used as the control gate is formed in thesecond well region.
 5. The method of claim 1, wherein a method offorming the tunnel layer and the inter-gate dielectric layer comprises:forming a dielectric material layer over the substrate; removing aportion of the dielectric material layer to form an exposed substrate,wherein a residual portion of the dielectric material layer comprisesthe inter-gate dielectric layer; and forming a tunnel layer over theexposed substrate.
 6. The method of claim 1, wherein a method of formingthe source region and the drain region comprises: forming a deeply dopedregion in the substrate corresponding to one side of the floating gateand under the tunnel layer; and forming the source region and the drainregion in the substrate at two sides of the floating gate and under thetunnel layer, wherein the source region is formed in the deeply dopedregion.
 7. The method of claim 1, further comprising forming a denselydoped region in the doped region used as the control gate.